In recent years, with the reduction in size and weight for electronic devices, laminated ceramic capacitors have been used widely which have a small size and allow high capacitance to be obtained. These laminated ceramic capacitors are each configured so that, for example, as shown in FIG. 1, internal electrodes 12 provided in a ceramic laminated body (laminated ceramic element) 10 are stacked with ceramic layers (dielectric ceramic layers) 11 interposed therebetween, and that a pair of external electrodes 13a, 13b are provided on both end surfaces of the ceramic laminated body 10 so as to provide electrical connections to the internal electrodes 12 exposed alternately at the opposite end surfaces.
Further, in these laminated ceramic capacitors, BaTiO3 based ceramic materials which have a high dielectric constant are commonly used as the dielectric layers.
Furthermore, as the BaTiO3 based ceramic materials, those with various accessory constituents, for example, rare-earth elements, Mg, etc. added are used for the purpose of improving characteristics such as temperature characteristics, insulation properties, reliability (life characteristics).
In addition, in order to achieve a balance between temperature characteristics and reliability (life characteristics) while keeping the temperature characteristics and reliability controllable, a crystal structure referred to as a so-called core-shell structure has been also adopted in which accessory constituents are mostly present as a solid solution in surface layer parts of ceramic grains (crystal grains), whereas the accessory constituents are hardly present as a solid solution in the crystal grains.
For example, Patent Document 1 proposes a laminated ceramic capacitor in which dielectric layers are composed of a sintered body of ceramic grains including a core part and a shell part surrounding the core part, the shell part of the ceramic grains contains: one or two or more acceptor elements selected from Mn, V, Cr, Co, Fe, Ni, Cu, and Mo; Mg; and a rare-earth element (Ho, Sc, Y, Gd, Dy, Er, Yb, Tb, Tm, Lu), and the concentration of the acceptor elements contained in the shell part is increased from the core-shell boundary toward the grain boundary (see Patent Document 1).
However, in the case of a laminated ceramic capacitor using, for dielectric layers, such a ceramic dielectric as disclosed in Patent Document 1, the use of the capacitor, for example, under an environment at a high temperature or a high electric field intensity has the problem of decreased reliability (life characteristics). Therefore, the development of dielectric materials has been actually desired which are able to constitute laminated ceramic capacitors which are further excellent in life characteristics.
Patent Document 1: Japanese Patent Application Laid-Open No. 2001-230149